Hydraulic boost device with auxiliary fluid supply

ABSTRACT

A hydraulic brake booster is disclosed which provides a power assist to the vehicle operator during a brake application. Pressurized hydraulic fluid is supplied to the booster from the vehicle&#39;&#39;s power steering pump. A charging valve carried in the booster housing permits flow of fluid into an accumulator when the fluid pressure level at the booster inlet exceeds the fluid pressure level in the accumulator. When flow of fluid to the inlet is terminated the charging valve is opened during a brake application to permit flow of fluid from the accumulator to the booster thereby allowing normal operation of the booster for a limited number of brake applications.

AUXILIARY FLUID SUPPLY United States Patent [151 3,638,528

Lewis Feb. 1, 1972 [54] HYDRAULIC BOOST DEVICE WITH PrimaryExaminer-Edgar W. Geoghegan Attorney-Ken C. Decker and Flame, Hartz,Smith & Thomp- [72] Inventor: Richard L. Lewis, South Bend, lnd. son

[73] Assignee: The Bendix Corporation [22] Filed: June 17, 1970 [57]ABSTRACT A hydraulic brake booster is disclosed which provides a power[211 App!' 47066 assist to the vehicle operator during a brakeapplication. Pressurized hydraulic fluid is supplied to the booster fromthe [52] [1.8. CI ..9l/6, 60/5 l 60/54.6 E vehiclcs power steering pump.A charging valve carried in the [III- booster housing permits flow ofinto an accumulator [53] Field of Search ..60/5 l 546 P, 52 B; 91/6 whenthe fluid pressure level at the booster inlet exceeds the fluid pressurelevel in the accumulator. When flow of fluid to [56] References Cltedthe inlet is terminated the charging valve is opened during a brakeapplication to permit flow of from the accumulator to the boosterthereby allowing normal operation of the l l Garrison et al. l X bo terfor a number of brake applications 3,131,538 5/1964 Schultz et al.........60/5l 3,133,417 5/ i 964 Hager ..60/5l 13 Claims, 5 Drawing FiguresI I] 7 a v a w I A 78 f 82 26 24- Z I l J 55 i /2 PATENTEDFEB 11212 333sum 1 or 2 l N VEN TOR. R/CHARD L LEW/5 ATTORNEY PATENTEU FEB I B SHEEY2 OF 2 I N VEN'IOR. RICHARD L. LEW/5 fi Wyn /04 /06 ATTORNEY HYDRAULICBOOST DEVICE WITH AUXILIARY FLUID SUPPLY BACKGROUND OF THE INVENTIONThis invention relates to a vehicle hydraulic system which includes ahydraulic brake booster.

Because of their smaller size and lower weight, hydraulic brake boostersare expected to be used in lieu of vacuum boosters in vehicles havingpower-assisted brakes. Such a device uses the pressurized fluid producedby the vehicles power steering pump to provide a hydraulic assist to thevehicle operator when the brakes are applied. However, if a malfunctionterminates flow of fluid to the booster, the powerbraking assist is lostimmediately and the vehicle operator must apply the brakes manually.Since existing vacuum boosters provide a vacuum reserve for a few brakeapplications after a power failure, vehicle operators expect some powerreserve so that a power assist is provided even after the engine stopsoperating.

SUMMARY OF THE INVENTION Therefore, an important object of my inventionis to provide a fluid reserve for a hydraulic brake booster that canoperate the latter even after the vehicles engine ceases to operate orif a malfunction in the vehicles hydraulic system terminates flow offluid to the booster.

Another important object of my invention is to provide a charging valvethat permits flow of fluid to the accumulator when the system isfunctioning normally and that permits flow of fluid from the accumulatorto the booster when flow of fluid from the pump to the booster isterminated.

Another important object of my invention is to design a charging valvethat may be installed within the booster housmg. i

A still further object of my invention is to furnish a charging valvethat opens to permit flow of fluid from the accumulator to the boosterwhen the valve that controls flow of fluid from the inlet of the boosterinto the working chamber thereof travels an abnormal distance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a brakebooster made pursuant to the teachings of my present invention;

FIG. 2 is an enlarged longitudinal cross-sectional view taken along line22 of FIG. 1;

FIG. 3 is an enlarged transverse cross-sectional view taken along line3-3 of FIG. 1;

FIG. 4 is a longitudinal cross-sectional view taken along line 44 ofFIG. 3 with portions of the hydraulic system shown schematically;

FIG. 5 is an enlarged, fragmentary view of that portion of my brakebooster enclosed by the dashed lines in FIG. 2.

DETAILED DESCRIPTION Referring now to the drawings, a brake boosterincludes a housing 12 having an inlet port 14, an outlet port 16, and areturn or exhaust port 18. The outlet port 16 is communicated to theinlet of a power steering gear 20, and the outlet port of the latter iscommunicated to the inlet of a power steering pump 22, as is the exhaustport l8, of the brake booster 10. The outlet of the pump 22 iscommunicated to the inlet port 14 of the booster 10. A spool valve 24 isslidable in a bore 26 and controls communication between the ports 14,16 and 18 and a boost chamber 28, also within the housing 12. Details ofthe construction and operation of the valve 24 will be describedhereinafter.

A boost piston 30 is slidable in a bore 32 within the housing 12. A rod34 interconnects the piston 30 with a standard master cylinder (notshown) mounted on the left side of the housing 12. Movement of thepiston 30 to the left viewing FIG. 2 develops pressure in the mastercylinder in the normal manner for applying the vehicles brakes. A returnspring 36 yieldably urges the piston 30 to the right viewing FIG. 2,toward the brake release position.

An operator-operated control rod 38 is slidably mounted in yet anotherbore 40 within the housing 12. One end of the rod 38 is attached to theusual brake pedal (not shown) mounted in the vehicle operator'scompartment. The other end of the rod 38 is slidably received in a blindbore 42 in the piston 30. The rod 38 extends through a stamping 43. Thestamping 43 is pivotally mounted in slots 44 in pair of levers 46 bypins 48. One end of the levers 46 is pivotally mounted to a bracket 50mounted on the piston 30 by pivots 52, and the other end of the levers46 are pivotally secured to the spool valve 24 as at 54. A spring 56yieldably urges an abutment 58 on the rod 38 into engagement with thestamping 43 so that the rod and sleeve move together as a unit when thebooster is functioning normally. The construction and operation of thepiston 30, rod 38, stamping 43 and levers 46 is described in detail incopending U.S. application Ser. No. 35,800, filed May 8, 1970, owned bythe assignee of the present invention and incorporated herein byreference.

The booster 10 illustrated in the drawings is shown in the brake releaseposition. In this position, a spring 60 urges an abutment 62 on thespool valve 24 against a shoulder 64 on the housing 12. While the spoolvalve is so disposed, fluid in the chamber 28 is vented to thelow-pressure side of the pump 22 through longitudinal passage 66 andradial passages 68 in the valve 24, grooves 70 and 72 in the valve 24and housing 12 respectively, and the outlet port 18. Fluid flowing intothe inlet 14 is communicated to the outlet 16 through groove 74 in thehousing 12 and groove 76 in the spool valve 24. Flow of fluid from theinlet 14 to the chamber 28 is terminated while the spool valve isdisposed in the brake release position since the fluid path between thegroove 76 and groove 74 is blocked. Details of the construction andoperation of the spool valve 24 are disclosed in copending U.S. Pat.application Ser. No. l3,4l5, filed Feb. 24, 1970, owned by the assigneeof the present invention and incorporated herein by reference.

A second bore 78 is disposed perpendicularly to the bore 26, and one endof the bore 78 is in fluid communication with the groove 76. The bore 78isldisposed in substantially the same transverse plane as is the inletport 14, but is circumferentially spaced from the latter. The other endof the bore 78 is in fluid communication with a fluid storage device oraccumulator 80. The accumulator 80 may be of any suitable design wellknown to those skilled in the art, such as that disclosed in U.S. Pat.No. 3,282,786 owned by the assignee of the present invention andincorporated herein by reference. An accumulator charging valve,generally indicated at 82 is housed in the bore 78 for controlling flowof fluid between the accumulator 80 and the bore 26.

Charging valve 82 includes a circumferentially extending valve seatmember 84 defining a passage 86 extending therethrough. A valve member88 is yieldably urged into engagement with the valve seat 84 by a spring90 to close the passage 86, thereby preventing flow of fluid through thevalve 82. Spring 90 also urges a metering member 92 against a tube seat94 which receives the conduit connecting the bore 78 to the accumulator80. Metering member 92 includes a plurality of radially extendingpassages 95 and a restrictive orifice 96 that controls the volume offluid flowing into the accumulator 80. A plunger 98 is slidably disposedin the lower part of the bore 78. Longitudinally extending channels 100are provided in the plunger 98 to permit flow of fluid through the bore78. A stern 102 projects from one end of the plunger 98 and extendsthrough the passage 86 for engagement with the valve member 88 when theplunger is shifted upwardly in the bore 78. The other end of the plunger98 slidably engages the spool valve 24. Valve 24 has a substantiallyconstant diameter section 104 and a sloped section 106 of constantlyincreasing diameter, presenting a conical camming surface.

MODE or OPERATION FIGS. 2, 4, and 5 illustrate the position of the spoolvalve 24 when the vehicles brakes are released. Assuming normaloperation of the pump 22, fluid will flow into the inlet 14 and out ofthe outlet 16 to operate the power steering gear 22. A portion of thefluid flowing into the inlet will flow through the channels 100 on theplunger 88 and, if the pressure of the fluid at the inlet exceeds thefluid pressure in the accumulator 80 by an amount necessary to overcomethe force of spring 95, fluid in the bore 78 will urge the valve member88 off of the seat 86. Fluid will then flow past the valve 82, throughthe passages 95 and orifice 96, and into the accumulator 80 where it isstored for future use as will be hereinafter explained.

When the vehicle operator applies the vehicles brakes, the control rod38 is urged to the left viewing the figures. Since the rod 38 isconnected to the levers 46 through the stamping 43, movement of the rod38 will pivot the levers 40 about the pivots 52, thereby shifting thevalve 24 to the left viewing the figures. As the valve 24 is shifted,fluid communication between the grooves 70 and 72 is terminated, therebyisolating the boost chamber 28 from the exhaust port 18. Simultaneously,flow of fluid is initiated from the groove 76 into the groove 72 andinto the boost chamber 28 through the passages 68 and 66. Thehigh-pressure fluid thereby admitted into the chamber 28 acts againstthe end of the piston 30, forcing the latter to the left viewing thefigures to apply the vehicles brakes. When the operator releases thebrakes, springs 36 and 60 return the piston and valve 24 to the brakerelease position illustrated in the figures.

As the valve 24 is shifted toward the position communicating fluid fromthe inlet 14 to the chamber 28, the plunger 98 remains in slidingengagement with the constant diameter section 104 of the valve 24, andtherefore, does not move within the bore 78. However, should fluidcommunication be terminated to the inlet 14 because, for example, thevehicle engine ceases to operate, the valve 24 is shifted by the vehicleoperator a small additional distance to engage the camming surface 106with the bottom of the plunger 98, forcing the latter upwardly in thebore 78. As the plunger 98 is shifted, the stem 102 engages the valvemember 88 to force the latter off of the seat 84. Fluid pressure in theaccumulator then forces the member 92 away from the seat 94 to permitfluid to flow from the accumulator 80 into the groove 76, and from thereinto the chamber 28 through the grooves 76 and 72 and passages 68 and 66to apply the brakes in the normal manner.

If the accumulator fluid supply is depleted, or if a malfunction in thevalve mechanism 24 prevents movement of the latter, spring 56 yieldswhen the vehicle operator depresses the brake pedal to permit the rod 38to move relative to the lever 46, the abutment 58 moving away from thestamping 43. The end of the rod 38 engages the end of the blind bore 42to provide a mechanical link between the master cylinder and the brakepedal, permitting the operator to apply the vehicle s brakes manually.

I claim:

1. In a vehicle hydraulic system:

a hydraulic boost device including a housing having an inlet, an outlet,a first bore communicating the inlet with the outlet, and a chamber influid communication with the inlet; 1

piston means shiftable in said chamber;

a pressure source in fluid communication with said inlet;

first valve means shiftable in said housing from a first position inwhich substantially all of the fluid flowing into the inlet is directedto the outlet toward a second position, said first valve meanscommunicating successively higher fluid pressure levels into saidchamber as the first valve means is shifted toward said second position;

operator-actuated means for actuating said first valve member;

means for storing fluid under pressure in fluid communication with saidhousing; and

second valve means for controlling fluid communication between thestorage means and the chamber and shiftable from a first position inwhich flow of fluid from the storage means to the bore is prevented to asecond position permitting fluid communication between the storage meansand the bore;

said first valve means including means to shift said second valve meansto its second position upon movement of the first valve means to itssecond position when fluid flow to said inlet is reduced.

2. The invention of claim 1:

said means to shift said second valve means including a camming surfaceon said first valve means; and

a plunger operably connected to said first and second valve means, saidplunger being shifted by said camming surface to shift said second valvemeans to its second position.

3. The invention of claim 2:

said first valve means being shiftable within a first bore communicating the inlet with the outlet;

a member projecting into said bore slidably engaging said first valvemeans;

said member shifting said second valve means from its first position toits second position upon movement of the first valve means to its secondposition.

4. The invention of claim 2:

said first valve means being shiftable in a first bore within thehousing communicating the inlet and outlet;

said housing defining a second bore therewithin in fluid communicationwith said first bore and with said fluid storage means;

said second valve means being housed in said second bore;

and

means operatively engaging said first valve means for shifting saidsecond valve means to its second position when said first valve means ismoved to its first position.

5. The invention of claim 2:

said first valve means being shiftable in a first bore communicating theinlet with the outlet;

said housing defining a second bore therewithin in fluid communicationwith said first bore to communicate the inlet and with said fluidstorage means;

said second valve means including a valve seat mounted in said secondbore and a valve member yieldably urged into engagement with said valveseat to prevent flow of fluid between the storage means and the firstbore, but moving from said seat to permit flow of fluid from the firstbore to the storage means when the fluid pressure level at the inletexceeds the fluid pressure level in the storage means; and

means operatively connecting said first valve means and said valvemember for forcing the latter off said seat when the first valve meansis shifted past its second position to permit flow of fluid from theaccumulator to the bore.

6. The invention of claim 5:

said valve seat being annular to define a passage extendingtherethrough, said valve member being yieldably urged into a positionclosing said passage;

said connecting means being a plunger movable within said housing uponsaid movement of the first valve means to its second position.

7. The invention of claim 6:

said first valve means having a substantially constant diameter sectionand a tapered section presenting a camming surface extending from saidconstant diameter section;

said plunger slidably engaging said constant diameter section as saidfirst valve means is shifted from said first position, said cammingsurfaces moving said plunger within said second bore to lift the valvemember off the seat when said second valve means is shifted to itssecond position.

8. The invention of claim 6:

said plunger being slidable in said second bore and having a projectingportion extending through the passage defined by the valve seat forengagement with the valve member when the plunger is moved to lift themember off of the seat.

9. The invention of claim 8:

said plunger having channel means extending therethrough to permit flowof fluid through the plunger between the second valve means and saidbore.

10. The invention of claim 5; and

resilient means in said second bore yieldably urging said valve memberagainst said valve seat.

1 l. The invention of claim 2; and

a plunger movable in said housing for shifting said second valve meansto its second position upon movement of the first valve means past itssecond position.

12. The invention of claim 11:

said first valve means having a substantially constant diameter sectionand a tapered section presenting a camming surface extending from saidconstant diameter section;

said plunger slidably engaging said constant diameter section when saidfirst valve means is shifted from said first position, said cammingsurface moving said plunger within said second bore to shift said secondvalve means to its second position when said second valve means isshifted to its second position.

13. The invention of claim 11:

said plunger having channel means extending therethrough to permit flowof fluid through the plunger between the second valve means and saidchamber.

1. In a vehicle hydraulic system: a hydraulic boost device including a housing having an inlet, an outlet, a first bore communicating the inlet with the outlet, and a chamber in fluid communication with the inlet; piston means shiftable in said chamber; a pressure source in fluid communication with said inlet; first valve means shiftable in said housing from a first position in which substantially all of the fluid flowing into the inlet is directed to the outlet toward a second position, said first valve means communicating successively higher fluid pressure levels into said chamber as the first valve means is shifted toward said second position; operator-actuated means for actuating said first valve member; means for storing fluid under pressure in fluid communication with said housing; and second valve means for controlling fluid communication between the storage means and the chamber and shiftable from a first position in which flow of fluid from the storage means to the bore is prevented to a second position permitting fluid communication between the storage means and the bore; said first valve means including means to shift said second valve means to its second position upon movement of the first valve means to its second position when fluid flow to said inlet is reduced.
 2. The invention of claim 1: said means to shift said second valve means including a camming surface on said first valve means; and a plunger operably connected to said first and second valve means, said plunger being shifted by said camming surface to shift said second valve means to its second position.
 3. The invention of claim 2: said first valve means being shiftable within a first bore communicating the inlet with the outlet; a member projecting into said bore slidably engaging said first valve means; said member shifting said second valve means from its first position to its second position upon movement of the first valve means to its second position.
 4. The invention of claim 2: said first valve means being shiftable in a first bore within the housing communicating the inlet and outlet; said housing defining a second bore therewithin in fluid communication with said first bore and with said fluid storage means; said second valve means being housed in said second bore; and means operatively engaging said first valve means for shifting said second valve means to its second position when said first valve means is moved to its first position.
 5. The invention of claim 2: said first valve means being shiftable in a first bore communicating the inlet with the outlet; said housing defining a second bore therewithin in fluid communication with said first bore to communicate the inlet and with said fluid storage means; said second valve means including a valve seat mounted in said second bore and a valve member yieldably urged into engagement with said valve seat to prevent flow of fluid between the storage means and the first bore, but moving from said seat to permit flow of fluid from the first bore to the storage means when the fluid pressure level at the inlet exceeds the fluid pressure level in the storage means; and means operatively connecting said first valve means and said valve member for forcing the latter off said seat when the first valve means is shifted past its second position to permit flow of fluid from the accumulator to the bore.
 6. The invention of claim 5: said valve seat being annular to define a passage extending therethrough, said valve member being yieldably urged into a position closing said passage; said connecting means being a plunger movable within said housing upon said movement of the first valve means to its second position.
 7. The invention of claim 6: saId first valve means having a substantially constant diameter section and a tapered section presenting a camming surface extending from said constant diameter section; said plunger slidably engaging said constant diameter section as said first valve means is shifted from said first position, said camming surfaces moving said plunger within said second bore to lift the valve member off the seat when said second valve means is shifted to its second position.
 8. The invention of claim 6: said plunger being slidable in said second bore and having a projecting portion extending through the passage defined by the valve seat for engagement with the valve member when the plunger is moved to lift the member off of the seat.
 9. The invention of claim 8: said plunger having channel means extending therethrough to permit flow of fluid through the plunger between the second valve means and said bore.
 10. The invention of claim 5; and resilient means in said second bore yieldably urging said valve member against said valve seat.
 11. The invention of claim 2; and a plunger movable in said housing for shifting said second valve means to its second position upon movement of the first valve means past its second position.
 12. The invention of claim 11: said first valve means having a substantially constant diameter section and a tapered section presenting a camming surface extending from said constant diameter section; said plunger slidably engaging said constant diameter section when said first valve means is shifted from said first position, said camming surface moving said plunger within said second bore to shift said second valve means to its second position when said second valve means is shifted to its second position.
 13. The invention of claim 11: said plunger having channel means extending therethrough to permit flow of fluid through the plunger between the second valve means and said chamber. 